Ques : What is Private networks ?

Private IP addresses are used in private networks managed by single authority. Private IP addresses are reusable among private networks i.e. private IP address used in one private network can be reused in another private network. Private IP addresses are not routable in the public Internet; that is they are not recognized by public routers. Therefore, hosts with private IP address cannot  communicate with public networks directly, there is a need of network address translation (NAT) system for this purpose.